Crosman 1377 advice

[--ped--]

other way round on the barrel the phase 3 barrels use a 1/4" probe and the phase 1 and 2 use a 5/16" probe with a sharper angle on the leade in which is the same on both .177 and .22 barrels
think a lot of the .177's were smooth bore but some were rifled and yes it is very faint

[Modski66]

I will be interested in how it groups when I put it back together.
When I pushed a pellet down the barrel, it does leave a faint rifling mark, but more worryingly, during the journey, it goes stiff then free, then stiff and free a number of times...

[--ped--]

try pushing a few cig filters through the barrel with a light ceaning soloution as often the barrels get full of crusty oil from people excessively using pelgun oil
I prefer a tad of hydraulic oil every now and again on the pivots

[Modski66]

Having read about the Canadian spec valve on the latest models, I didn't think there would be a relief hole on early examples. I did check on the back face of the valve - no hole, but as I was doing a trial fit today, I saw a hole on the SIDE of the valve, venting into the trigger space.
That will be part of my low fps accounted for then!

[--ped--]

is it directly opposite the exhaust port and is it a brass or aluminium valve

[Modski66]

It is directly opposite the transfer port, and the valve is brass.

[--ped--]

just thread it and Loctite a grub screw in it

[Modski66]

Glad you said that, I did it yesterday!

With the valve being an original design, it has the aluminium spacer between the nrv and valve spring. If I replaced the spacer with something hollow, would it make any significant difference to the available volume of pressurised air, and the resulting fps?

[--ped--]

yes it will increase volume
rather than fit a spacer fit a longer spring from either a current 1377 or use a crosman sear spring(only use for them as they're crap as a sear spring)
what you'll find is that you have to pump a bit more but it will be easier to do
I prefer using the high volume low pressure approach other how yours is now with a low volume and high pressure

[Modski66]

You sound like a pneumatics engineer....

[--ped--]

no just worked on a lot of crosman pumpers from vintage to modern

[Modski66]

The 1377 is back together for a functional test, and it certainly functions now! It has quite a bit of poke...
Not sure about the barrel condition though, shots are not grouping well, but that might be that the front sight is very skinny and difficult to keep central in the rear notch.
I am going to trial modify the front blade to test out my theory. Not keen on trying to replace this phase one barrel...

[--ped--]

lighten the sear spring it usually helps accuracy I don't do a kit for phase 1 frames but do for phase 2 onward and 22xx frames

[Modski66]

I have squashed the spring in a vice and fitted a modified 22lr case as a guide. Can I trim a couple of coils off without ruining it?

[--ped--]

if it has a phase 1 frame it already has a guide and the sear springs on these are much lighter than the later phase 2 and current frame